The present invention relates to a method of perfectly dicing a flat workpiece, for example a flat substrate made of quartz, silicon or the like on which LCD (Liquid Crystal Display) elements, solid state imaging devices such as CCD (Charge Coupled Device) elements, IC (Integrated Circuit) elements and the like are arranged, by for example a rotary blade to obtain the individual LCD elements, solid state imaging devices such as CCD elements, IC elements and the like; and an apparatus used for the method.
A related art method of and apparatus for dicing a workpiece will be first described with reference to FIG. 2.
FIG. 2 is a schematic side view of a related art dicing apparatus, with parts partially cutaway.
Referring to FIG. 2, reference numeral 1 indicates an apparatus for dicing a substrate (usually called "wafer", and hereinafter referred to as "wafer") made of quartz, silicon or the like on which many LCD elements, solid state imaging devices such as CCD elements, IC elements and the like are formed so as to manufacture the LCD elements, solid state imaging devices such as CCD elements, IC elements and the like. In FIG. 2, a wafer S composed of a quartz substrate, on the surface of which LCDs are formed, is used as a workpiece.
The dicing apparatus 1, while partially shown in the figure, includes a table 2 on which the wafer S as a flat workpiece is mounted in a horizontal state; a rotary blade 3 disposed over the table 2 movably in the vertical direction, which is finely adjustable in height and rotatable around a rotating axis 3A in the direction of an arrow R; and a drive unit (not shown) capable of advancing/retreating the rotary blade 3 while rotating it in a state in which the table 2 is fixed, that is, the wafer S is fixed in the horizontal state, or a drive unit (not shown) capable of rotating the rotary blade 3 at a specified height and moving the table 2 and the wafer S held in the horizontal state in the X-direction and the Y-direction.
The wafer S, which is a workpiece to be diced, has a front surface on which many LCD elements are formed in a matrix and a back surface stuck with a dicing tape T as an adhesive member. The dicing tape T is composed of a film base member B made of a plastic tape, on the surface of which a layer A of an adhesive Ab (hereinafter, referred to simply as "adhesive layer") is formed. The film base member B has a thickness of for example about 80 .mu.m, and the adhesive layer A has a thickness of for example about 10 .mu.m. An adhesive force (peeling strength) of the adhesive is selected in consideration of the strength and thickness of the wafer S, and it is usually in a range of from 100 to 1500 g for a tape width of 20 mm.
The adhesive layer A of the dicing tape T is directly stuck on the back surface of the wafer S.
The separation of the wafer S into the individual LCD elements using the dicing apparatus 1 is performed as follows. The wafer S is mounted and fixed on the table 2 in a horizontal state with the dicing tape T side down; the rotary blade 3 is rotated in the direction of an arrow R; and the wafer S stuck with the dicing tape T is diced along a dicing line usually having a width of about 170 .mu.m between the LCD elements while the table 2 is moved in the x-direction and Y-direction, to a thickness equivalent to the total of the entire thickness of the wafer S and about a half of the thickness of the adhesive layer A. The LCD elements are thus separated from each other, but are stuck on the dicing tape T which is not cut yet.
The related art method of and apparatus for dicing a workpiece, however, has a disadvantage. Specifically, chips (silicon, quartz) Da of the wafer S and chips Db of the adhesive of the adhesive layer A are, during dicing, scattered by a rotating force of the rotary blade 3, and adhere on the surface of a portion, near the dicing line, of the wafer S. Of these chips Da and Db adhering on the wafer S, the chips Da of the wafer S can be removed by cleaning using a dicing water or the like; however, the chips Db of the adhesive once adhering on the surface of the wafer S cannot be removed by simple cleaning, if the adhesive has a high adhesive force. Such chips Db cause a vital dust failure for the LCDs, solid state imaging device such as CCDs, or ICs which are presently advanced in integration and fine-geometries.